V4L/DVB: em28xx: add Dikom DK300 hybrid USB tuner
[linux-2.6.git] / mm / backing-dev.c
index a7c6c56..0e8ca03 100644 (file)
@@ -1,15 +1,50 @@
 
 #include <linux/wait.h>
 #include <linux/backing-dev.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
 #include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/mm.h>
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/writeback.h>
 #include <linux/device.h>
 
+void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
+{
+}
+EXPORT_SYMBOL(default_unplug_io_fn);
+
+struct backing_dev_info default_backing_dev_info = {
+       .name           = "default",
+       .ra_pages       = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,
+       .state          = 0,
+       .capabilities   = BDI_CAP_MAP_COPY,
+       .unplug_io_fn   = default_unplug_io_fn,
+};
+EXPORT_SYMBOL_GPL(default_backing_dev_info);
 
 static struct class *bdi_class;
 
+/*
+ * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
+ * reader side protection for bdi_pending_list. bdi_list has RCU reader side
+ * locking.
+ */
+DEFINE_SPINLOCK(bdi_lock);
+LIST_HEAD(bdi_list);
+LIST_HEAD(bdi_pending_list);
+
+static struct task_struct *sync_supers_tsk;
+static struct timer_list sync_supers_timer;
+
+static int bdi_sync_supers(void *);
+static void sync_supers_timer_fn(unsigned long);
+static void arm_supers_timer(void);
+
+static void bdi_add_default_flusher_task(struct backing_dev_info *bdi);
+
 #ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
@@ -24,9 +59,29 @@ static void bdi_debug_init(void)
 static int bdi_debug_stats_show(struct seq_file *m, void *v)
 {
        struct backing_dev_info *bdi = m->private;
-       long background_thresh;
-       long dirty_thresh;
-       long bdi_thresh;
+       struct bdi_writeback *wb;
+       unsigned long background_thresh;
+       unsigned long dirty_thresh;
+       unsigned long bdi_thresh;
+       unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
+       struct inode *inode;
+
+       /*
+        * inode lock is enough here, the bdi->wb_list is protected by
+        * RCU on the reader side
+        */
+       nr_wb = nr_dirty = nr_io = nr_more_io = 0;
+       spin_lock(&inode_lock);
+       list_for_each_entry(wb, &bdi->wb_list, list) {
+               nr_wb++;
+               list_for_each_entry(inode, &wb->b_dirty, i_list)
+                       nr_dirty++;
+               list_for_each_entry(inode, &wb->b_io, i_list)
+                       nr_io++;
+               list_for_each_entry(inode, &wb->b_more_io, i_list)
+                       nr_more_io++;
+       }
+       spin_unlock(&inode_lock);
 
        get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
 
@@ -36,12 +91,22 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
                   "BdiReclaimable:   %8lu kB\n"
                   "BdiDirtyThresh:   %8lu kB\n"
                   "DirtyThresh:      %8lu kB\n"
-                  "BackgroundThresh: %8lu kB\n",
+                  "BackgroundThresh: %8lu kB\n"
+                  "WritebackThreads: %8lu\n"
+                  "b_dirty:          %8lu\n"
+                  "b_io:             %8lu\n"
+                  "b_more_io:        %8lu\n"
+                  "bdi_list:         %8u\n"
+                  "state:            %8lx\n"
+                  "wb_mask:          %8lx\n"
+                  "wb_list:          %8u\n"
+                  "wb_cnt:           %8u\n",
                   (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
                   (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
-                  K(bdi_thresh),
-                  K(dirty_thresh),
-                  K(background_thresh));
+                  K(bdi_thresh), K(dirty_thresh),
+                  K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,
+                  !list_empty(&bdi->bdi_list), bdi->state, bdi->wb_mask,
+                  !list_empty(&bdi->wb_list), bdi->wb_cnt);
 #undef K
 
        return 0;
@@ -166,9 +231,300 @@ static __init int bdi_class_init(void)
        bdi_debug_init();
        return 0;
 }
-
 postcore_initcall(bdi_class_init);
 
+static int __init default_bdi_init(void)
+{
+       int err;
+
+       sync_supers_tsk = kthread_run(bdi_sync_supers, NULL, "sync_supers");
+       BUG_ON(IS_ERR(sync_supers_tsk));
+
+       init_timer(&sync_supers_timer);
+       setup_timer(&sync_supers_timer, sync_supers_timer_fn, 0);
+       arm_supers_timer();
+
+       err = bdi_init(&default_backing_dev_info);
+       if (!err)
+               bdi_register(&default_backing_dev_info, NULL, "default");
+
+       return err;
+}
+subsys_initcall(default_bdi_init);
+
+static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
+{
+       memset(wb, 0, sizeof(*wb));
+
+       wb->bdi = bdi;
+       wb->last_old_flush = jiffies;
+       INIT_LIST_HEAD(&wb->b_dirty);
+       INIT_LIST_HEAD(&wb->b_io);
+       INIT_LIST_HEAD(&wb->b_more_io);
+}
+
+static void bdi_task_init(struct backing_dev_info *bdi,
+                         struct bdi_writeback *wb)
+{
+       struct task_struct *tsk = current;
+
+       spin_lock(&bdi->wb_lock);
+       list_add_tail_rcu(&wb->list, &bdi->wb_list);
+       spin_unlock(&bdi->wb_lock);
+
+       tsk->flags |= PF_FLUSHER | PF_SWAPWRITE;
+       set_freezable();
+
+       /*
+        * Our parent may run at a different priority, just set us to normal
+        */
+       set_user_nice(tsk, 0);
+}
+
+static int bdi_start_fn(void *ptr)
+{
+       struct bdi_writeback *wb = ptr;
+       struct backing_dev_info *bdi = wb->bdi;
+       int ret;
+
+       /*
+        * Add us to the active bdi_list
+        */
+       spin_lock_bh(&bdi_lock);
+       list_add_rcu(&bdi->bdi_list, &bdi_list);
+       spin_unlock_bh(&bdi_lock);
+
+       bdi_task_init(bdi, wb);
+
+       /*
+        * Clear pending bit and wakeup anybody waiting to tear us down
+        */
+       clear_bit(BDI_pending, &bdi->state);
+       smp_mb__after_clear_bit();
+       wake_up_bit(&bdi->state, BDI_pending);
+
+       ret = bdi_writeback_task(wb);
+
+       /*
+        * Remove us from the list
+        */
+       spin_lock(&bdi->wb_lock);
+       list_del_rcu(&wb->list);
+       spin_unlock(&bdi->wb_lock);
+
+       /*
+        * Flush any work that raced with us exiting. No new work
+        * will be added, since this bdi isn't discoverable anymore.
+        */
+       if (!list_empty(&bdi->work_list))
+               wb_do_writeback(wb, 1);
+
+       wb->task = NULL;
+       return ret;
+}
+
+int bdi_has_dirty_io(struct backing_dev_info *bdi)
+{
+       return wb_has_dirty_io(&bdi->wb);
+}
+
+static void bdi_flush_io(struct backing_dev_info *bdi)
+{
+       struct writeback_control wbc = {
+               .bdi                    = bdi,
+               .sync_mode              = WB_SYNC_NONE,
+               .older_than_this        = NULL,
+               .range_cyclic           = 1,
+               .nr_to_write            = 1024,
+       };
+
+       writeback_inodes_wbc(&wbc);
+}
+
+/*
+ * kupdated() used to do this. We cannot do it from the bdi_forker_task()
+ * or we risk deadlocking on ->s_umount. The longer term solution would be
+ * to implement sync_supers_bdi() or similar and simply do it from the
+ * bdi writeback tasks individually.
+ */
+static int bdi_sync_supers(void *unused)
+{
+       set_user_nice(current, 0);
+
+       while (!kthread_should_stop()) {
+               set_current_state(TASK_INTERRUPTIBLE);
+               schedule();
+
+               /*
+                * Do this periodically, like kupdated() did before.
+                */
+               sync_supers();
+       }
+
+       return 0;
+}
+
+static void arm_supers_timer(void)
+{
+       unsigned long next;
+
+       next = msecs_to_jiffies(dirty_writeback_interval * 10) + jiffies;
+       mod_timer(&sync_supers_timer, round_jiffies_up(next));
+}
+
+static void sync_supers_timer_fn(unsigned long unused)
+{
+       wake_up_process(sync_supers_tsk);
+       arm_supers_timer();
+}
+
+static int bdi_forker_task(void *ptr)
+{
+       struct bdi_writeback *me = ptr;
+
+       bdi_task_init(me->bdi, me);
+
+       for (;;) {
+               struct backing_dev_info *bdi, *tmp;
+               struct bdi_writeback *wb;
+
+               /*
+                * Temporary measure, we want to make sure we don't see
+                * dirty data on the default backing_dev_info
+                */
+               if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list))
+                       wb_do_writeback(me, 0);
+
+               spin_lock_bh(&bdi_lock);
+
+               /*
+                * Check if any existing bdi's have dirty data without
+                * a thread registered. If so, set that up.
+                */
+               list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) {
+                       if (bdi->wb.task)
+                               continue;
+                       if (list_empty(&bdi->work_list) &&
+                           !bdi_has_dirty_io(bdi))
+                               continue;
+
+                       bdi_add_default_flusher_task(bdi);
+               }
+
+               set_current_state(TASK_INTERRUPTIBLE);
+
+               if (list_empty(&bdi_pending_list)) {
+                       unsigned long wait;
+
+                       spin_unlock_bh(&bdi_lock);
+                       wait = msecs_to_jiffies(dirty_writeback_interval * 10);
+                       schedule_timeout(wait);
+                       try_to_freeze();
+                       continue;
+               }
+
+               __set_current_state(TASK_RUNNING);
+
+               /*
+                * This is our real job - check for pending entries in
+                * bdi_pending_list, and create the tasks that got added
+                */
+               bdi = list_entry(bdi_pending_list.next, struct backing_dev_info,
+                                bdi_list);
+               list_del_init(&bdi->bdi_list);
+               spin_unlock_bh(&bdi_lock);
+
+               wb = &bdi->wb;
+               wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
+                                       dev_name(bdi->dev));
+               /*
+                * If task creation fails, then readd the bdi to
+                * the pending list and force writeout of the bdi
+                * from this forker thread. That will free some memory
+                * and we can try again.
+                */
+               if (IS_ERR(wb->task)) {
+                       wb->task = NULL;
+
+                       /*
+                        * Add this 'bdi' to the back, so we get
+                        * a chance to flush other bdi's to free
+                        * memory.
+                        */
+                       spin_lock_bh(&bdi_lock);
+                       list_add_tail(&bdi->bdi_list, &bdi_pending_list);
+                       spin_unlock_bh(&bdi_lock);
+
+                       bdi_flush_io(bdi);
+               }
+       }
+
+       return 0;
+}
+
+static void bdi_add_to_pending(struct rcu_head *head)
+{
+       struct backing_dev_info *bdi;
+
+       bdi = container_of(head, struct backing_dev_info, rcu_head);
+       INIT_LIST_HEAD(&bdi->bdi_list);
+
+       spin_lock(&bdi_lock);
+       list_add_tail(&bdi->bdi_list, &bdi_pending_list);
+       spin_unlock(&bdi_lock);
+
+       /*
+        * We are now on the pending list, wake up bdi_forker_task()
+        * to finish the job and add us back to the active bdi_list
+        */
+       wake_up_process(default_backing_dev_info.wb.task);
+}
+
+/*
+ * Add the default flusher task that gets created for any bdi
+ * that has dirty data pending writeout
+ */
+void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
+{
+       if (!bdi_cap_writeback_dirty(bdi))
+               return;
+
+       if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
+               printk(KERN_ERR "bdi %p/%s is not registered!\n",
+                                                       bdi, bdi->name);
+               return;
+       }
+
+       /*
+        * Check with the helper whether to proceed adding a task. Will only
+        * abort if we two or more simultanous calls to
+        * bdi_add_default_flusher_task() occured, further additions will block
+        * waiting for previous additions to finish.
+        */
+       if (!test_and_set_bit(BDI_pending, &bdi->state)) {
+               list_del_rcu(&bdi->bdi_list);
+
+               /*
+                * We must wait for the current RCU period to end before
+                * moving to the pending list. So schedule that operation
+                * from an RCU callback.
+                */
+               call_rcu(&bdi->rcu_head, bdi_add_to_pending);
+       }
+}
+
+/*
+ * Remove bdi from bdi_list, and ensure that it is no longer visible
+ */
+static void bdi_remove_from_list(struct backing_dev_info *bdi)
+{
+       spin_lock_bh(&bdi_lock);
+       list_del_rcu(&bdi->bdi_list);
+       spin_unlock_bh(&bdi_lock);
+
+       synchronize_rcu();
+}
+
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                const char *fmt, ...)
 {
@@ -187,9 +543,33 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                goto exit;
        }
 
+       spin_lock_bh(&bdi_lock);
+       list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
+       spin_unlock_bh(&bdi_lock);
+
        bdi->dev = dev;
-       bdi_debug_register(bdi, dev_name(dev));
 
+       /*
+        * Just start the forker thread for our default backing_dev_info,
+        * and add other bdi's to the list. They will get a thread created
+        * on-demand when they need it.
+        */
+       if (bdi_cap_flush_forker(bdi)) {
+               struct bdi_writeback *wb = &bdi->wb;
+
+               wb->task = kthread_run(bdi_forker_task, wb, "bdi-%s",
+                                               dev_name(dev));
+               if (IS_ERR(wb->task)) {
+                       wb->task = NULL;
+                       ret = -ENOMEM;
+
+                       bdi_remove_from_list(bdi);
+                       goto exit;
+               }
+       }
+
+       bdi_debug_register(bdi, dev_name(dev));
+       set_bit(BDI_registered, &bdi->state);
 exit:
        return ret;
 }
@@ -201,9 +581,61 @@ int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 }
 EXPORT_SYMBOL(bdi_register_dev);
 
+/*
+ * Remove bdi from the global list and shutdown any threads we have running
+ */
+static void bdi_wb_shutdown(struct backing_dev_info *bdi)
+{
+       struct bdi_writeback *wb;
+
+       if (!bdi_cap_writeback_dirty(bdi))
+               return;
+
+       /*
+        * If setup is pending, wait for that to complete first
+        */
+       wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
+                       TASK_UNINTERRUPTIBLE);
+
+       /*
+        * Make sure nobody finds us on the bdi_list anymore
+        */
+       bdi_remove_from_list(bdi);
+
+       /*
+        * Finally, kill the kernel threads. We don't need to be RCU
+        * safe anymore, since the bdi is gone from visibility. Force
+        * unfreeze of the thread before calling kthread_stop(), otherwise
+        * it would never exet if it is currently stuck in the refrigerator.
+        */
+       list_for_each_entry(wb, &bdi->wb_list, list) {
+               thaw_process(wb->task);
+               kthread_stop(wb->task);
+       }
+}
+
+/*
+ * This bdi is going away now, make sure that no super_blocks point to it
+ */
+static void bdi_prune_sb(struct backing_dev_info *bdi)
+{
+       struct super_block *sb;
+
+       spin_lock(&sb_lock);
+       list_for_each_entry(sb, &super_blocks, s_list) {
+               if (sb->s_bdi == bdi)
+                       sb->s_bdi = NULL;
+       }
+       spin_unlock(&sb_lock);
+}
+
 void bdi_unregister(struct backing_dev_info *bdi)
 {
        if (bdi->dev) {
+               bdi_prune_sb(bdi);
+
+               if (!bdi_cap_flush_forker(bdi))
+                       bdi_wb_shutdown(bdi);
                bdi_debug_unregister(bdi);
                device_unregister(bdi->dev);
                bdi->dev = NULL;
@@ -213,14 +645,26 @@ EXPORT_SYMBOL(bdi_unregister);
 
 int bdi_init(struct backing_dev_info *bdi)
 {
-       int i;
-       int err;
+       int i, err;
 
        bdi->dev = NULL;
 
        bdi->min_ratio = 0;
        bdi->max_ratio = 100;
        bdi->max_prop_frac = PROP_FRAC_BASE;
+       spin_lock_init(&bdi->wb_lock);
+       INIT_RCU_HEAD(&bdi->rcu_head);
+       INIT_LIST_HEAD(&bdi->bdi_list);
+       INIT_LIST_HEAD(&bdi->wb_list);
+       INIT_LIST_HEAD(&bdi->work_list);
+
+       bdi_wb_init(&bdi->wb, bdi);
+
+       /*
+        * Just one thread support for now, hard code mask and count
+        */
+       bdi->wb_mask = 1;
+       bdi->wb_cnt = 1;
 
        for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
                err = percpu_counter_init(&bdi->bdi_stat[i], 0);
@@ -245,6 +689,20 @@ void bdi_destroy(struct backing_dev_info *bdi)
 {
        int i;
 
+       /*
+        * Splice our entries to the default_backing_dev_info, if this
+        * bdi disappears
+        */
+       if (bdi_has_dirty_io(bdi)) {
+               struct bdi_writeback *dst = &default_backing_dev_info.wb;
+
+               spin_lock(&inode_lock);
+               list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
+               list_splice(&bdi->wb.b_io, &dst->b_io);
+               list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
+               spin_unlock(&inode_lock);
+       }
+
        bdi_unregister(bdi);
 
        for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
@@ -259,13 +717,12 @@ static wait_queue_head_t congestion_wqh[2] = {
                __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
        };
 
-
-void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
+void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
 {
        enum bdi_state bit;
-       wait_queue_head_t *wqh = &congestion_wqh[rw];
+       wait_queue_head_t *wqh = &congestion_wqh[sync];
 
-       bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
+       bit = sync ? BDI_sync_congested : BDI_async_congested;
        clear_bit(bit, &bdi->state);
        smp_mb__after_clear_bit();
        if (waitqueue_active(wqh))
@@ -273,29 +730,29 @@ void clear_bdi_congested(struct backing_dev_info *bdi, int rw)
 }
 EXPORT_SYMBOL(clear_bdi_congested);
 
-void set_bdi_congested(struct backing_dev_info *bdi, int rw)
+void set_bdi_congested(struct backing_dev_info *bdi, int sync)
 {
        enum bdi_state bit;
 
-       bit = (rw == WRITE) ? BDI_write_congested : BDI_read_congested;
+       bit = sync ? BDI_sync_congested : BDI_async_congested;
        set_bit(bit, &bdi->state);
 }
 EXPORT_SYMBOL(set_bdi_congested);
 
 /**
  * congestion_wait - wait for a backing_dev to become uncongested
- * @rw: READ or WRITE
+ * @sync: SYNC or ASYNC IO
  * @timeout: timeout in jiffies
  *
  * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
  * write congestion.  If no backing_devs are congested then just wait for the
  * next write to be completed.
  */
-long congestion_wait(int rw, long timeout)
+long congestion_wait(int sync, long timeout)
 {
        long ret;
        DEFINE_WAIT(wait);
-       wait_queue_head_t *wqh = &congestion_wqh[rw];
+       wait_queue_head_t *wqh = &congestion_wqh[sync];
 
        prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
        ret = io_schedule_timeout(timeout);